ST ST1S03A User Manual

1.5 A, 1.5 MHz adjustable, with inhibit function

Features

■ Step-down current mode PWM (1.5 MHz) DC-

DC converter

■ 2 % DC output voltage tolerance

■ Internal soft start for start-up current limitation

and power on delay of 50-100 µs

■ Typical efficiency: > 85 %

■ Inhibit function

■ 1.5 A output current capability

■ Not switching quiescent current: max 1.5 mA

over temperature range

■ Switch V

■ Uses tiny capacitors and inductors

■ Available in DFN6D 3x3 exposed pad

: max 200 mV @ I

DS

= 750 mA

SW

ST1S03A

step-down switching regulator

DFN6D (3x3 mm)

Description

The ST1S03A is a step down DC-DC converter
optimized for powering low-voltage digital core in
HDD applications and, generally, to replace the
high current linear solution when the power
dissipation may cause an high heating of the
application environment. It provides up to 1.5 A
over an input voltage range of 3 V to 5.5 V. An high
switching frequency (1.5 MHz) allows the use of
tiny surface-mount components: as well as the
resistor divider to set the output voltage value,
only an inductor, a schottky diode and two
capacitors are required. Besides, a low output
ripple is guaranteed by the current mode PWM
topology and by the use of low ESR SMD ceramic
capacitors. The device is thermal protected and
current limited to prevent damages due to
accidental short circuit. The ST1S03A is available
in DFN6D (3x3 mm).

Table 1. Device summary

Order codes Packaging Package

ST1S03APUR Tape and reel DFN6D (3x3 mm)

ST1S03AIPUR Tape and reel DFN6D (3x3 mm)

June 2008 Rev 6 1/14

www.st.com

14

ST1S03A

Contents

1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6 Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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ST1S03A Diagram

1 Diagram

Figure 1. Schematic diagram

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Pin configuration ST1S03A

2 Pin configuration

Figure 2. Pin configuration (top view)

ST1S03A

Table 2. Pin description

Pin n° Symbol Name and function

1

2 GND System ground

3 SW Output of the internal power switch

4

5

6 N.C./INH Not connected / or inhibit

V

V

IN_SW

V

FB

IN_A

Voltage of feedback

Power supply for the mosfet switch

Power supply for the analog circuit

ST1S03AI

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ST1S03A Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

IN_SW

V

IN_A

V

INH

SWITCH

Voltage

V

FB

I

VFB

T

J

T

STG

T

LEAD

Positive power supply voltage -0.3 to 7 V

Positive power supply voltage -0.3 to 7 V

Max voltage of inhibit pin -0.3 to 6 V

Max voltage of output pin -0.3 to 7 V

Feedback voltage 2.5 V

Common mode input voltage 1 mA

Max junction temperature 150 °C

Storage temperature range -25 to 150 °C

Lead temperature (soldering) 10 sec 300 °C

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these conditions is not implied.

Table 4. Thermal data

Symbol Parameter Value Unit

R

thJA

R

thJC

Thermal resistance junction-ambient 55 °C/W

Thermal resistance junction-case 10 °C/W

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